1. Field of the Invention
The invention concerns surgical lasers and their controllers as well as methods for the treatment of an eye lens, especially for the treatment of presbyopia.
2. Description of the Related Art
Starting at the age of about 45 years, there begins a continuous decrease of the ability of the lens of the human eye to accommodate. This is manifested by the occurrence of farsightedness due to age (presbyopia). Due to its decreasing elasticity, the eye lens is no longer able to thicken sufficiently as necessary for sharp imaging of near objects on the retina. Unaffected by the decreasing elasticity, the ciliary muscle as well as the capsule sack surrounding the lens of the eye, both usually remain active and elastic.
Krueger et al., Ophthalmology 108 (2001): 2123-2129 treated human eye lens enucleated with a neodymium:YAG laser by irradiation with laser pulses having a pulse energy of 2.5 to 7.0 mJ thus producing an annular pattern of cavitation bubbles in the inside of treated lens. By this treatment, they were able to achieve an increase in the elasticity of the lens. However, for effective treatment of presbyopia, it is desirable to increase the elasticity further. In addition, during the treatment, large and long-lived cavitation bubbles were produced, which made it more difficult to measure the change of the bending of the lens. Furthermore, development of shockwaves and strong heating of the lens occurred, which cannot be tolerated by living patients.
It was proposed in DE 199 40 712 A1 to produce bubble fields inside an eye lens for the treatment of presbyopia, these bubbles being filled by fluid. The little bubbles are intended to loosen the lens material and increase the flexibility of the lens. However, the results of such a treatment were still found to be unsatisfactory.